Photographic film base



y 9, 1939- J. G.-DAV|DSON 2,157,384

PHOTOGRAPHIC FILM BASE Filed NOV. 7, 1936 IZZ/ -//2 PART/AL POLYV/NVL ACEML RES/N] INVENTOR JOSEPH G. DAVIDSON ATTORNEY Patented May '9, 1939 PATENT OFFICE PHOTOGBAPHIC FILM BASE Joseph G. Davi dson, Scarsdale, N. Y., assignor to Carbide and'Carbon Chemicals Corporation, a corporation of New York Application November '1, 1936, Serial No. 109,667

1s Claimsl This invention relates to a film base such as is commonly employed for the support of photographic emulsions. It provides an improved material of this class which possesses many desirable 5 features not heretofore found in photographic film bases.

The materials used in the past have been of the rigid type, such as glass, or of the flexible type which includes those formed of plasticized cellulose nitrate (Celluloid) and cellulose acetate. The use of glass for this purpose is very limited because its fragility, weight, and bulkiness render it difiicult to handle, and it is impossible to use glass photographic supports under many condi- 16 tions, such as in the production of motion pictures. Celluloid is highly inflammable, but it is used at present to a lai'ge extent as a base for photographic films which are not subjected to heat. To overcome this fire hazard, particularly 20 in moving picture machines'where the film is severely heated, films formed of cellulose acetate have been substituted for Celluloid, and the products of this type are known as safety film.

However, the only advantage cellulose acetate has over plasticized cellulose nitrate (Celluloid) is its slow-burning characteristics, and owing to its lack of toughness it has been adopted only where safety is a factor. No plasticizer has ever been found for cellulose acetate which imparts 0 to it the properties which camphor gives to the nitrate. Most of the best plasticizers for cellulose acetate, such as dimethyl or diethyl phthlates or triacetin, have relatively high vapor pressures. Accordingly, plasticized cellulose acetate films tend to become brittle with age, and this brittleness can be overcome only by humidifying the film prior to use.

The ideal photographic film base should be transparent, water-proof, tough, flexible, non-ex- 0 plosive and slow-burning, and should hold its dimensions when stressed under fairly high temperatures. It should have no cold flow or permanent stretch under small stresses, or shrinkage on storage, and should not react with photographic emulsions. It should be readily soluble in cheap solvents so that fabrication into sheets may be accomplished by casting (spreading a solution to a uniform depth upon a smooth surface and removing the film upon evaporation of the. solvent) and its surface should possess resistance to scratching. v

It is an object of this invention to provide material which meets the requirements specified above more nearly than any film support pro- 56 posed heretofore.

The object of this invention may. be accomplished by the use of transparent films made of certain partial polyvinyl acetal resins; that is, polyvinyl resins in which there are both acetal and hydroxyl groups, but substantially no others. These resins are thermoplastic materials which are adequately resistant to moisture, and which are inert with respect to photographic emulsions or chemicals used in their manufacture or development. Sheets made frpm the partial poly- 19 vinyl acetal resins of this invention have been found to possess more nearly the characteristics \desired in an ideal film base than do any other o the available materials for this use.

The accompanying drawing diagrammatically 1. illustrates the invention, in which the emulsion I0 is supported upon the film base II. The film base It is made of the partial polyvinyl acetal resins described herein, and the emulsion l0 may contain particles of silver or light-sensitive salts, or it maycomprise any. cinematographic image.

These partial polyvinyl acetal resins give tough films even when unplasticized, and they are less thermoplastic than the corresponding vinyl ester resins. For the most satisfactory results the films are made from partial polyvinyl acetal resins which have a high average macromolecular weight. Generally, those resins made from polyvinyl alcohol, or a polyvinyl ester, having an average molecular weight of at least 7,000 are desirable, and resins made from polyvinyl alcohol, or esters having molecular weights of about 7,000 to about 12,000 are preferred. Those resins derived from polyvinyl bodies of molecular weights in excess of about 25,000 are stronger, and are more desirable. when it is necessary to produce exceptionally tough films. (Molecular weights referred to' herein are calculated by means of Staudingers formula from viscosity determinations on solutions of the materials.) Such resins are, in general, insoluble in water, but are soluble in alcohols and water-alcohol mixtures.

The thermoplasticity of these resins is proportional to both the quantity and molecular weight of the aldehyde reacted with the polyvinyl alcohol. The more aldehyde that is reacted, the more thermoplastic the resins become, so that completely reacted polyvinyl acetal resins have ,about the same thermoplasticity as the corresponding polyvinyl esters. In a similar manner, the longer the aldehyde chain that is reacted the more thermoplastic the resins become until the partial acetal resins of six and'seven carbon atom aldehydes are as thermoplastic as the complete acetals of the lower aldehydes.

Water absorption of the resins is also related directly to the amount and molecular weight oi the aldehyde reacted. For example, the partial polyvinyl acetals of formaldehyde have very high water absorption while partial, polyvinyl acetal resins} jacet'a lized with an {aldehyde fflofj "higher molecularweight have lower water ab sorption,

phatic aldehydes result in products. which are more desirable than thejunsat' atedf aldeh and, in general, the straight-chained saturated; aliphatic aldehydes containing from two to six carbon atoms are specifically suitable resins are the partial polyvinyl acetals of acetaldehyde, propionaldehyd'e,

7 although croton'aldehyde,* benzaldehyde,- 'aldol, and "other aldehydes may 'be used. i It is possible,

of course, tomake partial polyvinyl acet'a'lsin which two ormore different aldehydes" are com- -bined in the same polymeric molecule.- Of *these various resins,- those formed from""propionaldehyde andbutyraldehydeare preferred.

The'd'egreeto which the hydroxyl groups of the polyvinylalcohol have been combined with aldehyde maybe indicated directly as percent acetalization, and the optimum degree'of acetalization for the resins of this invention-is range give'nabove. rangefor propionaldehyde and butyraldehyde is from about 33% to 80%; Since both the quantity and kind of aldehyde used influence the characteristics ofthe resin, the preferred coinposition for aresinfrom ariyparticular aldehyde would be somewhat more limited than the general For example, the preferred approximately 50% to 80%"acetalization, while for 'ahexaldehyde' resin 'the preferred range i from about 33% toua 50 i Y W The partial polyvinyl acetal resins maybe prepared by 'any'o'fthe many known ways, andth'ese resins are suitable' fornse in this invention however-they-Jare'made; Forexamplathe aldehyde may be reacted directly with the polyvinylalconor in-1 the presence %'.of an acidic substance, or

the partial acetal may. be. formed'from a: vinyl ester by the simultaneous alcoholysis of the. ester 1 and partial.acetalization ofthe polyvinyl alcohol forrnedl Resins made by th'e' latter method were e'mployed'iin. the development of this" invention. T-he zfollowin'glexamples ..arei given by. .Way of illustration. x1111.-

Aretha 1 iIia i nk n fi e ih gfli following materials and allowing thepolutionas P e e is t d. o mer 9 Parts .I-Iigh .viscositypolyvinyl acetates-resin; Propionaldehydeng Me e l' 7dwithiwat'er, redissolved in methanol, neutralized,

and further purified by several preclpitatlons.

. Analysis showed the resin tovbe approximately 58% acetalizeda Example H l "15" has; its asserted purified wine acid;

referred. Examples "butyraldhyde, valeraldehyde, and hexaldehyde,

j mmdeh de} Sulfuric sem method given in Example I. The following materials were used in its preparation.

Parts by weight High viscosity polyvinyl acetate resin v774 Butyraldehyde 381 Methanol Analysis indicated the resin to be about 66% The aldehydes used may be of any type. Bot aromatic and aliphatic are useful, but theali phatic aldehydes are preferred. "saturated ali Parts by weight Medium.viscosityfpolyvinyl acetate resin 225 Butyraldehyde 105 Methanol 1,750

v @110 in. a ut 6.2%." e ad- Example 1V A resin wasprepared from" the 'fol lowin glmaterials by a procedure similar to that us'ed in EX- ample'r, t. Part byw ie Medium viscosity polyvinyl acetat resin" 120.0

Methanol; I

1 'I'he resin, upon analysisg-was found-tube about 70.%'acetalized.; l

If the resins areto be usedforkmoving picture films," a resinprepared 'as in- Examples I oreIV 'would'be suitable.1-0nthe other hand, rollxor cut films, that .are not subjectedto as'high temperature as moving I picture films may 1 be made; from Examples ,II .'or III. i

:0 Since. these resinsipossess a' high degree'of clarity, films made from them arenot'lir'nited to 7 any particular "thickness;.andthey. may be fabricated fromctheresin by. any of the usual methods :knownc-in. the -art, suchaas calenderinggtcasting etc. -Ho w'ever; for the sake-.ofieconomy, the .films need-not be made rthicker. than .thoseinow; used .;forphotographic emulsion. supports 7 unless cun- .usual strength is. necessary; andlfilms; even thinher. have been found satisfactory. Arparticularly suitable thickness was .found. to be .about0.003 inch; orslightlyrthinner, thanv the-flexible graphiofilm bases now on the-market. .-This ;new;photographic filmisupporti is much superior tonprior art materials 1 in :that itis slow photoburning, sufiiciently water-resistant; flexible,-ex-

,tremelytough; and highly-resistant to deteriora- ,tion; A, surprising fact ;isthat even: though; the

resin containscombined aldehyde it is inert .with M e peq i to raph emul i an the chemiaa s u dwi pr c ss n ms he. mer it e -r 101 tort-ano e: mod a e Stre s at ai y h h. tem e ure h s mos 1 9 d flow. o a permanent ,stretch under small stresses, does ot shrink on storage and its v surface-is resistant to r hin.e-y ,5 Ma o m tion end t e f o ra hic film may, of course,be made by; this process. li film b se, o a t for ha ht-s nsi iv composition, may be made with-.any,de gree of translucency although; transparent- .filr n is generally preferred. Furthermore the composition,

or cOatingLb rne by th'etfilm base, either before or after photochemicalreaction and subsequent developing and fixing, may vary in degree of ran u cy f o ranspar ncy o c mp t acetalized from about 50 percent to about 80 p y- Such v r i n in th o t a of percent with proplonaldehyde and having an u se. e ral y pr duced by the inclu on in t average macromolecular weight of at least 10,000. c at of subs a t a y opaque. m ute pa e 8. As an article of manufacture, a non-explocontaining silver. I sive, slow-burning photographic film base having Various m difications wil llfl il t e v the properties of toughness, clarity and retention to those Skilled in the art, and such variations of flexibility with age in an unusual degree, said are included within the scope of this invention film base comprising a partial polyvinyl acetal as defined by the appended claims. resin in which the polyvinyl alcohol has been I claim: 'acetallzed from about 50 percent to about 80 l. A non-explosive, slow-burning photographi percent with propionaldehyde and having an fi m a h v t e pr p r s o toughness, average macromolecular weight of at least 25,000. clarity and retention of flexibility with age in an 9. As an article of manufacture, a non-explollllllellal ree, a d fil ba e co pr s slve, slow-burning photographic film base having tifle es hstfly identical w t the properties of toughness, clarity and retention wa r n lu pr d t f the re ction of p iyof flexibility with age in an unusual degree, s'aid ny alcohol w h n aldehyde, wh h P d fllm base comprising a partial polyvinyl acetal contains both acetal group and p yv y alcohol resin in which the polyvinyl alcohol has been hydrcxyl groups a d antia y oacetalized from about 50 per cent to about 80 2 A no xp1cs v .s1ow-burni g p o ap ic percent with butyraldehyde and having an averfl base having the Properties of toughness, age macromolecular weight of at least 10,000. clarity and retention of flexibility with age in 10. A film comprising a non-explosive, slowa u u u l c ee. sa d fil base compr s n an burning film base bearing a coating which varies artificial resin substantially identical with the in degree of transluceney from transparency to w ll e Product Of the r n f D IY- opacity due to the presence in the coating of V y aieohol w th a sat r aliph ic l hy substantially opaque particles containing silver, which Product contains th M al d polyvinyl said fllm base having the properties of toughness, lc hol hydr x B ip and sub n l y no clarity and retention of flexibility with age in an others. unusual degree, and said film base comprising a m A non-explosive, u g P g p partial polyvinyl acetal resin in which the polyfllm base having the properties of toughness, vinyl alcohol has been acetalized between 50% clarity and retention of flexibility with age in nd with ropionaldehyde. an unusual d cr said film ba e mpr s a 11. A fllrn comprising a non-explosive, slowartificial resin substantially identical with the burning mm a e bearing a coating whichvarles Weller-insoluble Product f the reaction of p yin degree of translucency from transparency to v nyl al h l w th a satu straight-chain opacity due to the presence in the coating of subaiiphhtic aldehyde. wh Product while-ills 130th stantially opaque particles containing silver, said acetal and polyvinyl alcohol hydroxyl groups and film base having the properties of toughness, ub n i ly no h clarity and retention of flexibility with age in an 4- A nonxp s v wurn g Photographic unusual degree, and said fllm base comprising a film ba e having the Properties of toughness, partial polyvinyl acetal resin in which the polyy and te t of flexibility with 8 in all vinyl alcohol has been acetalized between perunusual de ree. said fi a e o l ri ll n cent and percent with butyraldehyde. artificial resin substantially identical with the 12, As an ti of anufacture, a non-explowater-insoluble product of the reaction of polysive, slow-burning film consisting of a transvinyl a cohol wit p p n which prcdlucent coating produced from a light-sensitive uc contains b th acetal and Polyvinyl 81001101 photographic emulsion supported on the surface hydr x g p substantially no oilhel'sof a fllm base which is inert to photographic 5- A n nrexp v urn g photographic emulsions and to chemicals used in processing are film base having the properties of toughness, films, said film base having the properties of clarity and re n of flexibility w h s in toughness, clarity and retention of flexibility an unu defl tl fi base comprisihfl all with age in an unusual degree, and said film base ar ific l res substantially identical with the comprising a water-insoluble polyvinyl cetal water-inso ub e produ f t reaction of p resin containing acetal and polyvinyl alcohol hyvinyl alcohol with butyraldehyde, which product droxyl groups and substantially no others.

contains both acetal and polyvinyl h l 1 8- 13. A non-explosive, slow-burning film base droxyl groups so substantially no others. particularly adapted for use in moving picture 6. A non-explosive, slow-burning photographic film, said film base. having the properties oi? film base having the properties of toughness, toughness, clarity and retention of flexibility w clarity and retention of mummy with age in with age in an unusual degree under the condian unusualkdmee' said m We compmm tions to which moving picture film is subjected, partial poiwlnyl mm resm m which the polysaid fllm base comprising an artificial resin subg g j g fj fi fifi gg ggg mm 33 stantlally identical with the product or the reaca'cmr tion of polyvinyl alcohol with propionaldehyde, As an w ,f m fi i'fifigfi which product is acetalized from about 58 perzi i ki g a and retention cent to about '70 percent, and which product conf fl ggfut mu age in unusual degree talus additionally polyvinyl alcohol hydroxyl 0 e y groups and substantially no others. nlm base comprising a partial polyvinyl a 8m G D VI N resin in. which the polyvinyl alcohol has been J 

